The present invention relates to a device for inspecting the interior of an enclosure, especially (but not solely) for inspecting material contained in the enclosure.
The following description illustrates an application of the device to the inspection of the upper surface of the burden in a blast furnace. This is done, however, by way of example and without implying any limitation of the applicability of the device. A device according to the invention can be used for observing the interior of any enclosure.
There is a well-recognized interest in observing what goes on in a blast furnace at the upper surface of the charge or burden, e.g. the evolution of the shape of this surface, the distribution of surface temperatures from its centre to its periphery, and the appearance of hot spots or cold zones. These indications allow the operation of the blast furnace to be improved, this depending on appropriate addition of coke, ore, and fluxes as well as on accurate distribution of these materials across the whole of the upper surface of the burden.
The value of all data is of course subordinate to the fact of being able to correctly observe the burden by means of a device which is as reliable as possible. This condition cannot easily be met, because the space above the burden in the blast furnace may contain a compressed gas (for example, at a pressure of 2 kg per cm.sup.2 ) and is practically always very dusty.
In order to observe the charge inside a blast furnace, various devices have already been suggested which are generally of the type in which scanning occurs inside a practically fixed device, or of telemetric type. In most cases, these devices permit observation of the burden in a blast furnace through an inspection window of transparent material permanently cleaned from inside. The increase in back pressure inside blast furnaces has made the use of such inspection windows more risky. The inspection windows are difficult to clean satisfactorily by scraping. Moreover, it is difficult to ensure a jet of gas on the inner face of the inspection hole in order to clean it.